System for detecting and correcting color vision deficiencies based on critical fusion frequency spectral scanning

Abstract

Method for detecting color vision deficiencies of a subject by determining his or her spectral sensitivity curve, wherein the spectral sensitivity curve is determined by critical fusion frequency spectral scanning at predetermined discrete narrow bands of wavelengths, preferably being blue, green, orange and red. The compensation of the color vision deficiency occurs by using a compensation color determined on the basis of differences between a standard sensitivity curve and the measured one. In each wavelength where such differences are experienced, the intensity of the light source generating that wavelength is increased or decreased in accordance with the extent and sign of the difference, and the compensation color is obtained by illuminating all light sources.

What is claimed is:  
     
       1. Method for detecting color vision properties of a subject by determining his or her spectral sensitivity curve, characterized by carrying out said determining step by critical fusion frequency scanning, wherein the critical fusion frequency is measured with a discrete number of color lights radiating at respective narrow wavebands, and each of said color lights have an intensity that corresponds to the component intensity of a white light with a predetermined color temperature in said narrow waveband of said color light. 
     
     
       2. The method as claimed in claim  1 , wherein the combined light of all of said color lights results in said white light, and the method further comprising the steps of measuring the critical fusion frequency of said combined light, and calculating the quotients of the component critical fusion frequency values and of the critical fusion frequency of said combined white light to obtain normalized critical fusion frequency values, and using said normalized critical fusion frequency values at said determining step. 
     
     
       3. The method as claimed in claim  2 , wherein the color of said light sources being blue, green, orange and red with respective medium wavelengths being about 435, 535, 615 and 660 nm. 
     
     
       4. The method as claimed in claim  2  for obtaining the compensation color of the determined vision deficiency, characterized by the steps of establishing the differences between a standard spectral sensitivity curve determined previously from subjects with normal vision and the curve of the subject under test at each of said bands, and in the bands where a difference has been established, increasing or decreasing the intensity of the associated light source corresponding to the extend and sign of said difference, and generating said compensating light by simultaneously illuminating all of said light sources with the so adjusted intensity. 
     
     
       5. Method for providing a correction lens for a subject with color vision deficiency by utilizing the compensation color as determined by claim  4 , characterized by the step of painting said lens by means of a conventional lens painting method using said compensation color for defining the color of the painting. 
     
     
       6. Method for providing a correction lens for a subject with color vision deficiency by utilizing the compensation color as determined by claim  4 , characterized by the steps of: taking a diapositive picture of said compensating light, separating the color layer from the diapositive, inserting said color layer between two parts of a glued lens, and connecting said parts together so that said layer gets sandwiched therebetween. 
     
     
       7. Method for correcting the color vision deficiency of a subject when viewing a color display by utilizing the compensation color as determined by claim  4 , characterized by the step of modifying the color transfer function of said display in accordance with said compensation color. 
     
     
       8. Apparatus for carrying out the method as claimed in claim  2 , characterized by comprising a lighting unit ( 14 ) composed of light emitting diodes (B, G, O, R) or groups thereof emitting light in said bands, respectively; a hollow tube ( 17 ) receiving said lighting unit ( 14 ) at one end region; an ocular lens ( 15 ) arranged at the frontal other end of said tube; a diapositive slide arranged across said tube and having a transparent pattern allowing passage of light towards those parts of the retina of the subject looking through said lens, where vision is provided purely by cones; a current generator circuit ( 40 ) including respective controlled current generators associated with said diodes (B, G, O, R), a pulse generator coupled to control inputs of said current generators for controlling pulsation of current flowing through said diodes; and a potentiometer adjustable by the subject under test for adjusting the repetition frequency of said pulse generator. 
     
     
       9. The apparatus as claimed in claim  8 , wherein the currents of said current generator circuit ( 40 ) are adjustable in separate predetermined steps for each of said light sources, and the currents at each step being interrelated in such a way that the simultaneous illumination of all diodes result in a white light with a predetermined color temperature. 
     
     
       10. The apparatus as claimed in claim  9 , wherein said steps correspond to equal intensity step sensations by the subject when viewing the light generated by the excitation of said diodes by said currents. 
     
     
       11. The apparatus as claimed in claim  8 , further comprising a display ( 44 ) providing information on the results of the examinations, a keyboard ( 43 ) for adjusting the mode of operation, a microprocessor ( 42 ) for controlling and coordinating operation, and a memory ( 42 ) for storing actual values of the critical fusion frequency of the subject at each measurement as well as for storing normalized values of said critical fusion frequencies relative to a basic critical fusion frequency obtained by illumination with white light. 
     
     
       12. The apparatus as claimed in claim  8 , comprising a set of color slides that can be inserted in the place of said diapositive slide, said color slides comprise standard tables for testing color vision. 
     
     
       13. The method as claimed in claim  1 , wherein said critical fusion frequency measurements being carried out when the eye of the subject has adapted to the actual intensity used, and the light of said light source being directed to areas of the retina where there is a pure cone vision.